add zipper postwalk.

Author: Yannick Scherer

src/rewrite_clj/zip.clj

@@ -67,7 +67,8 @@
    subedit-node subedit-> subedit->>]
 
   [rewrite-clj.zip.walk
-   prewalk]
+   prewalk
+   postwalk]
 
   [rewrite-clj.zip.whitespace
    whitespace? linebreak?

src/rewrite_clj/zip/walk.clj

@@ -23,3 +23,21 @@
   ([zloc p? f]
    (->> (partial prewalk-subtree p? f)
         (subedit-node zloc))))
+
+(defn postwalk-subtree
+  [p? f loc]
+  (let [nloc (m/next loc)
+        loc' (if (m/end? nloc)
+               loc
+               (m/prev (postwalk-subtree p? f nloc)))]
+    (if (p? loc')
+      (or (f loc') loc')
+      loc')))
+
+(defn ^{:added "0.4.9"} postwalk
+  "Perform a depth-first post-order traversal starting at the given zipper location
+   and apply the given function to each child node. If a predicate `p?` is given,
+   only apply the function to nodes matching it."
+  ([zloc f] (postwalk zloc (constantly true) f))
+  ([zloc p? f]
+   (subedit-node zloc #(postwalk-subtree p? f %))))

test/rewrite_clj/zip/walk_test.clj

@@ -23,3 +23,17 @@
         (-> (iterate #(w/prewalk % not-vec? inc-node) root)
             (nth 3)
             base/root-string) => "[3 [4 5 6] 7]"))
+
+(fact "about zipper tree postwalk."
+      (let [root (base/of-string "[0 [1 2 3] 4]")
+            wrap-node #(e/edit % list 'x)
+            wrap-node-p #(if (sq/vector? %) (wrap-node %) %)]
+        (-> root
+            (w/postwalk identity)
+            base/root-string) => "[0 [1 2 3] 4]"
+        (-> root
+            (w/postwalk wrap-node-p)
+            base/root-string) => "([0 ([1 2 3] x) 4] x)"
+        (-> root
+            (w/postwalk sq/vector? wrap-node)
+            base/root-string) => "([0 ([1 2 3] x) 4] x)"))